Role of fines on cohesive behavior of mine tailings inferred from critical shear stress

Abstract

The significance of fines on the cohesive behavior of mine tailings has been investigated by examining the incipient motion of the tailings. Sixteen laboratory experiments were performed in a Plexiglas laboratory annular column on re-constituted mine tailings under a 50 cm water cover. Re-suspension was produced by a Teflon stirrer and the velocity field in the column was characterized using a laser Doppler velocimeter (LDV). The pressure change in the boundary layer was also measured with a Preston tube. It was observed that the nondimensional critical shear stresses showed deviation from those of the noncohesive model results at a fines content greater than 50%–55%. An empirical relation that shows the relation between the boundary shear stress deviation and the percent fines in the tailings was proposed. Regression analysis of the experimental results showed that a power law relationship could reasonably be used to describe the relation between the measured nondimensional excess bed shear stress and the erosion rate. It is proposed that the value of β (the erosion rate constant) could be taken as 1 for mine tailings that show cohesive behavior.